This invention relates generally to methods and apparatus for detection of signal light parameters, and more particularly to methods and apparatus for detecting and reporting flashing signal light failures occurring at remote locations.
Railroads are now utilizing remote monitoring of signal locations as a tool for more rapid diagnosis of signaling problems. When such problems are promptly corrected, improved efficiency and safety of operations results.
Current methods of monitoring flashing warning lights in railroad applications are labor intensive to install and to calibrate, and do not provide a reliable, unambiguous, long-term indication of lamp performance.
One condition presently monitored at signal locations is the presence of AC power. Although backup battery systems are often employed, battery power is sometimes exhausted before AC power is restored and before maintenance personnel are alerted to the problem. To reduce the likelihood of this occurrence, backup battery systems having large reserve capacity are used. However, if an outage is persistent and goes undetected, as for example, when there is an open circuit breaker at the signal location, the first indication of trouble may occur only when the signal location is altogether nonfunctional. Timely reporting of AC power outages would help avoid such delays.
Techniques most often employed to report AC power outages measure bulk current through primary conductors supplying external lamps, and draw inferences to determine an exact number of bulbs that are operating correctly. These circuits are highly sensitive and the current detection components themselves (Hall effect devices) are prone to aging drift and nonlinearity.
Additional measures have been taken to alleviate problems associated with extended loss of AC power at highway crossings. For example, crossings are designed with separate operating battery and control battery systems. The battery systems have different capacities, so that, when AC power is lost, the operating battery is depleted first. The highway crossing is configured so that, upon depletion of the operating battery, the crossing is activated continuously. Ideally, the crossing will be reported as malfunctioning before the control battery is also depleted. Active crossings are also provided with indicator lights that are continuously lit when AC power is available. Employees are instructed to report an AC power off condition immediately to a dispatcher when they observe that the indicator lamps are off. Equipment houses at active crossing locations are also labeled with site-specific information and a toll-free telephone number that can be used by the public for reporting crossing problems.
Even with measures now in place, however, the reporting of crossing problems is still primarily a manual process, with inherent inaccuracies and delays. It would be desirable if these inaccuracies and delays could be reduced or eliminated. Moreover, many other crossing conditions, such as battery voltages and lamp currents, and for highway crossings, gate operation and activation status, are of interest and should be monitored. It has been difficult, however, to obtain timely reports of these conditions from remote locations.